THE horse’s natural reproductive period coincides with the light-filled days of summer. The desire to breed mares early in the year means that many foals are born at a darker time of year than nature intended. This has consequences for breeding efficiency. Often, early foaling mares experience longer gestations, have smaller foals and can have trouble cycling post-foaling.
As well as hormones that control reproduction, lengthening daylight stimulates important growth hormones that allow foals to mature in utero and mares to produce more milk and good colostrum. Specifically, it is the blue light wavelengths from the sun that drive these seasonal hormonal changes. For successful breeding outcomes, timing is everything. In the thoroughbred sector, early ovulations mean the production of early season foals and increases the economic value of youngstock. Successful manipulation of the light cycle, the primary regulator of reproduction in horses, has permitted the advancement of the mare’s breeding season to meet industry timelines. By extending the mare’s daily exposure to artificial light from December, reproductive activity is brought forward and the breeding sheds are busy from February each year.